If Karma wanted to he could take legal action against the members of the "team". That letter was a blatant attempt at blackmail, which is against the law. He could likely threaten legal action and force them all off of the team. Despite whatever bad leadership Karma may or may not have shown, that letter is unexcusable! If you have a bad leader you either leave or speak to him about it, you don't attempt to blackmail him out of everything he's worked so hard for.
I don't know if Karma was a bad leader, but it doesn't matter. It was a free mod that the team was under no obligation to work on, they are completely in the wrong with that letter. It is extremely stupid and insulting, and I hope Karma takes legal action against them, at least to get them banned from using any material relating to the Troopers mod.
Just keep in mind, everyone, that blackmail is illegal and if the members of the team had a problem they should have left or spoken to Karma. So despite a possible lack of leadership by Karma (note possible) it is completely, and unexcusably, wrong what the team members did.